Radar device, and method of generating a radar image

ABSTRACT

A radar device includes a transmitter, a receiver and processing circuitry. The transmitter transmits a first pulse signal and a second pulse signal, a pulse width of the second pulse signal being wider than a pulse width of the first pulse signal. The receiver may receive a first reception signal including a reflection signal of the first pulse signal and a second reception signal including a reflection signal of the second pulse signal. The processing circuitry may be configured to compare, in a first section that is at least partly in a distance direction, a signal intensity of the first reception signal with a signal intensity of the second reception signal, and generate a display signal based on a result of the comparison.

CROSS-REFERENCE TO RELATED APPLICATION(S)

This application claims priority under 35 U.S.C. § 119 to JapanesePatent Application No. 2019-013806, which was filed on Jan. 30, 2019,the entire disclosure of which is hereby incorporated by reference.

TECHNICAL FIELD

The present disclosure relates to a radar device, and a method ofgenerating a radar image.

BACKGROUND

In recent years, from a viewpoint of effective use of radio waveresources, the solid-state radar device which uses a semiconductoramplifier (solid-state component) has been developed, instead of anelectron tube, such as a magnetron. Since the solid-state radar devicehas an advantage of downsizing, free of maintenance, etc., other thannarrowing the band, it is expected to be widely spread in future. Sincethe solid-state radar device is small in the transmission power comparedwith the radar device which uses the electron tube, S/N (signal tonoise) ratio of a reflection signal from a distant location is lowered(its detection performance deteriorates). In order to compensate thisproblem, a frequency-modulated pulse signal with a large pulse width(hereinafter, referred to as the “modulated pulse signal”) istransmitted, and pulse compression is carried out for the reflectionsignal from a target to perform processing for improving the S/N ratioof the reflection signal from the distant location (Supervised byTakashi Yoshida, “Revised Radar technology”, The Institute ofElectronics, Information and Communication Engineers of JAPAN, publishedon May 25, 1999, p.p. 275-280).

On the other hand, in case of a radar device of the type in whichtransmission and reception are switched with one antenna, since atransmission pulse signal transmitted to a receiver directly, receptionis not possible during transmission. Moreover, if the pulse width iswide, a blind zone in which the reflection signal cannot be received isproduced by the widened amount at an area near the radar device.Therefore, in order to improve the detection performance in thisimmediate-vicinity area, a method of alternately transmitting amodulated pulse signal with a wide pulse width and an unmodulated pulsesignal with a narrow pulse width periodically is devised. In case ofsuch a radar device, a radar image is generated based on the reflectionsignal of the unmodulated pulse signal in a short-distance section fromthe radar device, and a radar image is generated based on the reflectionsignal of the modulated pulse signal in a long-distance section from theradar device.

Meanwhile, a radar beacon (hereinafter, referred to as the “racon”) isinstalled at a route buoy of a major route close to a narrow aqueduct orland coast, etc. When a pulse signal is received from a radar devicemounted on a ship, the racon transmits a response signal at the samefrequency as the received pulse signal. This response signal isMorse-coded by amplitude modulation, and this Morse-coded responsesignal is displayed, together with an echo of the racon, in a radarimage in the distance direction from the echo (see FIG. 1A). Therefore,a crew can accurately grasp the route buoy etc. from the radar imagealso in a congested oceanic condition. As described above, the raconplays a significant role for assisting the navigation of the ship.

However, the echo based on the response signal from the raconcorresponding to the modulated pulse signal is elongated in the distancedirection in the radar image due to a pulse compression, and thus theresponse signal tends not to be displayed normally. Therefore, for asolid-state radar device described in WO2014/42134A1, the followingtechnique is proposed. This solid-state radar device detects theexistence of the response signal from the racon contained in thereception signal, and the response signal of the racon is displayednormally by expanding an area based on the unmodulated pulse signal withthe narrow pulse width in the radar image, for the direction whichincludes the response signal of the racon.

Meanwhile, although depending on specification, the racon may notrespond to the pulse signal with the wide pulse width (typically, thepulse signal having the pulse width of 2 microseconds or more).Therefore, although the racon responds to the unmodulated pulse signalwith a comparatively narrow pulse width, it does not often respond themodulated pulse signal with a wider pulse width. In such a case, asillustrated in FIG. 1B, the response signal of the racon cannot beacquired in the long-distance area corresponding to the modulated pulsesignal in the radar image, and the response signal will not bedisplayed. Note that since the solid-state radar device described inPatent Document 1 is the technology of normally displaying the responsesignal of the racon by detecting the response signal of the racon fromthe reception signal, it cannot solve in the first place the problemsother than what is caused by that the response signal does not returnfrom the racon.

SUMMARY

One purpose of the present disclosure is to provide a radar device, amethod of generating a radar image, and a radar image generatingprogram, which can more certainly receive a response signal from atransponder, such as a racon, and display the response signal in theradar image.

A radar device is provided. The radar device includes a transmitter, areceiver and processing circuitry. The transmitter is configured totransmit a first pulse signal and a second pulse signal, a pulse widthof the second pulse signal being wider than a pulse width of the firstpulse signal. The receiver is configured to receive a first receptionsignal including a reflection signal of the first pulse signal and asecond reception signal including a reflection signal of the secondpulse signal. The processing circuitry is configured to compare, in afirst section that is at least partly in a distance direction, a signalintensity of the first reception signal with a signal intensity of thesecond reception signal, and generate a display signal based on a resultof the comparison in the first section.

The processing circuitry may be further configured to generate thedisplay signal in the first section based on the first reception signalwhen the first reception signal has a larger signal intensity than thesecond reception signal, and generate the display signal in the firstsection based on the second reception signal when the second receptionsignal has a larger signal intensity than the first reception signal.

The processing circuitry may be further configured to compare a signalintensity of a synthetic signal of the first reception signal and thesecond reception signal with the signal intensity of the first receptionsignal in a second section closer to a transmitting location than thefirst section, and generate the display signal based on a result of thecomparison in the second section.

The processing circuitry may be further configured to generate thedisplay signal in the second section based on the synthetic signal whenthe synthetic signal has a larger signal intensity than the firstreception signal, and generate the display signal in the second sectionbased on the first reception signal when the first reception signal hasa larger signal intensity than the synthetic signal.

The first pulse signal may have a pulse width of less than 2microseconds, and the second pulse signal may have a pulse width of 2microseconds or longer.

The transmitter may be installed on an installation surface, and maytransmit through an antenna configured to rotate in a plane parallel tothe installation surface.

The first pulse signal may be an unmodulated signal and the second pulsesignal may be a modulated signal.

A method of generating a radar image, and a radar image generatingprogram may configured to cause a computer to execute the followingprocessing, are provided. The method of generating a radar imageincludes transmitting a first pulse signal and a second pulse signal, apulse width of the second pulse signal being wider than a pulse width ofthe first pulse signal, receiving a first reception signal including areflection signal of the first pulse signal and a second receptionsignal including a reflection signal of the second pulse signal,comparing, in a first section that is at least partly in a distancedirection, a signal intensity of the first reception signal with asignal intensity of the second reception signal, and generating adisplay signal based on a result of the comparison.

BRIEF DESCRIPTION OF THE DRAWINGS

The present disclosure is illustrated by way of example and not by wayof limitation in the figures of the accompanying drawings, in which likereference numerals indicate like elements and in which:

FIG. 1A is a view illustrating a radar image indicating a responsesignal of a racon according to a conventional technology;

FIG. 1B is a view illustrating a radar image indicating a responsesignal of a racon according to another conventional technology;

FIG. 2 is a view illustrating the entire configuration of a radar deviceaccording to one embodiment of the present disclosure;

FIG. 3 is a view illustrating a configuration of a primary partaccording to a generation of the radar image;

FIG. 4 is a view illustrating the radar image based on a first imagedata;

FIG. 5 illustrates graphs of waveforms, where Graph (A) is a waveform ofa first echo data, Graph (B) is a waveform of a second echo data, Graph(C) is a waveform of the first image data, and Graph (D) is a waveformof a second image data;

FIG. 6 is a view illustrating the radar image based on the second imagedata;

FIG. 7 is a flowchart illustrating a flow of the generation of the radarimage; and

FIG. 8 is a graph illustrating a mixed ratio of the first echo data andthe second echo data for generating the first image data according toone modification.

DETAILED DESCRIPTION

Hereinafter, a radar device, a method of generating a radar image, and aradar image generating program according to one embodiment of thepresent disclosure will be described with reference to the drawings.

<1. Configuration of Radar Device>

FIG. 2 illustrates a view of the entire configuration of a radar device1 according to this embodiment. The radar device 1 may be a device forassisting the navigation of a ship, and may be mounted on the ship. Theradar device 1 of this embodiment may be a solid-state radar devicewhich uses a semiconductor amplifier (solid-state component) instead ofan electron tube, such as a magnetron, and may have advantages ofnarrowing band, downsizing, and free of maintenance, etc. Note that thepresent disclosure may be applied to ships which typically travel onwater or sea which are referred to as surface ships, and may also beapplied to other types of ships including boats, dinghies, watercrafts,and vessels. Further, the present disclosure may also be applied, ifapplicable, to submarines, aircrafts, and spaceships, as well as anytypes of vehicles which travel on the ground, such as automobiles,motorcycles, and ATVs.

As illustrated in FIG. 2, the radar device 1 may include a radar antenna10, a transmitter 2 and a receiver 3 which are connected to the radarantenna 10 through a circulator 11, and a radar indicator 20 furtherconnected to the transmitter 2 and the receiver 3. The radar antenna 10may repeat operation of transmitting a pulse-shaped radio wave andreceiving a reflection wave on a target object, while rotating in aplane parallel to an installation surface of the radar device 1, therebyscanning 360° around the ship. The radar antenna 10 may be shared forthe transmission and the reception, and the transmitter 2, the radarantenna 10, and the receiver 3 may be connected to three ports of thecirculator 11. The radar indicator 20 may include a display unit 21, auser interface 22, a memory 23, and a controller 24. These parts 21-24may be mutually connected through a bus line so as to be communicatable.

The display unit 21 may be a user interface which displays a screen formainly presenting a variety of information to a user who is a crew, andmay be comprised of a liquid crystal display in this embodiment. Theuser interface 22 may be a user interface which receives variousoperations to the radar indicator 20 from the user, and may be comprisedof a keyboard, a trackball, and a touch panel overlaid on the displayunit 21.

The memory 23 may be a nonvolatile storage device comprised of a harddisk drive, a flash memory, etc. The controller 24 may be comprised of aCPU 30, a ROM 31, and a RAM 32, etc. The ROM 31 may store a program 40for causing the CPU 30 to execute various operations. The CPU 30 mayread and execute the program 40 in the ROM 31 to virtually operate as atransmission controlling module 24 a, a signal processing module 24 b, apulse synthesizing module 24 c, a comparing module 24 d, and a renderingmodule 24 e (see FIG. 3). The details of operations of these parts 24a-24 e will be described later. Note that the program 40 may be storednot in the ROM 31 but in the memory 23, or may be stored distributedlyin both the memory 23 and the ROM 31.

The radar device 1 which is the solid-state radar device may have smalltransmission power compared with the radar device which uses theelectron tube. Therefore, in order to compensate a fall of an S/N ratioof a reflection signal from a distant location, the radar device 1 maytransmit a modulated pulse signal with a wide pulse width which isfrequency modulated, and perform a pulse compression to the receptionsignal acquired by the transmission. In more detail, the receptionsignal may be correlated with a matched filter corresponding to themodulated pulse signal to detect a peak waveform of the correlationvalue. Note that as for the modulated pulse signal with the wide pulsewidth, a blind zone may occur near the radar device 1. In order tosecure a detection performance in this area, the radar device 1 mayperiodically transmit the modulated pulse signal with the wide pulsewidth and the unmodulated pulse signal with a narrower pulse width whichis not frequency-modulated. Although not limited to this configuration,the unmodulated pulse signal may be implemented as a radio wave of theform called “P0N” and the modulated pulse signal may be implemented as aradio wave of the form called “Q0N” in this embodiment. Although notlimited to this configuration, the pulse width of the unmodulated pulsesignal may be from about 0.1 microsecond to about 1 microsecond and thepulse width of the modulated pulse signal may be from severalmicroseconds to about tens of microseconds in this embodiment. Forexample, if the pulse width of the modulated pulse signal is 10microseconds, a range of about 1,500 meters from the radar device 1 maybecome the blind zone. Although the details will be described later, aradar image generated in this embodiment may be mainly based on thesignal intensity of the reflection signal of the unmodulated pulsesignal in a short-distance area, and mainly based on the signalintensity of the reflection signal of the modulated pulse signal in along-distance area. Note that, in this description, unless particularlydescribed, “near (closer)” and “far (distant)” as used herein may be onthe basis of the radar device 1 (a transmitting location of the pulsesignal).

FIG. 3 is a view illustrating a configuration of a primary part whichperforms the generation of the radar image. The transmission controllingmodule 24 a may control operation of the transmitter 2 to controltransmission and reception periods of the modulated pulse signal, andtransmission and reception periods of the unmodulated pulse signal. Thetransmitter 2 may be comprised of a D/A converter, a mixer whichupconverts the transmission signal to a desired frequency band, and anamplifier which amplifies the upconverted transmission signal. The pulsesignal generated by the transmitter 2 may be supplied to the radarantenna 10 through the circulator 11. The radar antenna 10 may rotatewith beam directivity. Thus, the transmitter 2 may alternately transmitthe modulated pulse signal and the unmodulated pulse signal through theradar antenna 10 sequentially to various directions in thecircumferential direction centering on the radar device 1.

The receiver 3 may be comprised of an amplifier which amplifies thereception signal, a mixer which downconverts a signal of a desiredfrequency band included in the reception signal, various filters (LPF)and an A/D converter which carry out a quadrature detection of thedownconverted signal and output a complex signal. The receiver 3 mayreceive, through the radar antenna 10, alternately a reception signal(hereinafter, referred to as the “first reception signal”) including thereflection signal of the unmodulated pulse signal which is receivedduring a receiving period (hereinafter, referred to as the “firstreceiving period”) of the unmodulated pulse signal, and a receptionsignal (hereinafter, referred to as the “second reception signal”)including the reflection signal of the modulated pulse signal receivedduring a receiving period (hereinafter, referred to as the “secondreceiving period”) of the modulated pulse signal, sequentially fromvarious directions in the circumferential direction centering on theradar device 1. Note that, when the racon which received the pulsesignal from the radar antenna 10 transmits a response signal, thereception signal inputted into the receiver 3 may include the responsesignal of the racon. Here, when the pulse signal is received from theradar device, a frequency agile-type racon may transmit the responsesignal at the same frequency as the received pulse signal. This responsesignal may be Morse-coded by amplitude modulation. Depending on thespecification, the racon may mainly respond to the pulse signaltypically with a narrow pulse width of less than 2 microseconds, but itmay not respond to the pulse signal with the wide pulse width of 2microseconds or longer. Such a racon may return the response signal tothe unmodulated pulse signal according to this embodiment, but it maynot return the response signal to the modulated pulse signal with awider pulse width. Therefore, although the first reception signal duringthe first receiving period includes the response signal of the racon,the reception signal of the second reception signal during the secondreceiving period may not include the response signal of the racon.

The signal processing module 24 b may include a filter (e.g., LPF orBPF) having a pass band of a frequency width corresponding to about aninverted value of the pulse width of the unmodulated pulse signal. Thesignal processing module 24 b may apply signal processing to the firstreception signal during the first receiving period by using the filteretc. described above to extract echo data. The echo data based on thefirst reception signal (hereinafter, referred to as the “first echodata”) may be used mainly for generating the image data of theshort-distance area. However, the unmodulated pulse signal may betransmitted and received so as to cover the long-distance area as wellas the short-distance area, and the first echo data may be extracted bya length not only corresponding to the short-distance area but also thelong-distance area.

The signal processing module 24 b may include the matched filter inwhich a coefficient highly correlated with the modulated pulse signal isset. The signal processing module 24 b may apply signal processingincluding a pulse compression to the second reception signal during thesecond receiving period by using the matched filter etc. to extract theecho data. The echo data based on the second reception signal(hereinafter, referred to as the second echo data) may be used mainlyfor generating the image data of the long-distance area. Since thesecond reception signal which is pulse-compressed is the reflection waveof the modulated pulse signal, it may present a peak of the echo of themodulated pulse signal by the matched filter. That is, the echo with thelong pulse width corresponding to the pulse width of the modulated pulsesignal may be converted into one peak waveform which ispulse-compressed. The pulse-compressed peak waveform may indicate a peaklevel according to the pulse width of the modulated pulse signal. Sincethe modulated pulse signal is long in the pulse width compared with theunmodulated pulse, the S/N ratio may improve.

The pulse synthesizing module 24 c may synthesize the first echo dataand the second echo data outputted from the signal processing module 24b. At this time, the two kinds of echo data may be synthesized so thatthe first echo data forms the image data for the short-distance area andthe second echo data forms the image data for the long-distance area.The pulse synthesizing module 24 c may generate a first image data V1 (adisplay signal of the radar image) only by using the first echo dataamong the first echo data and the second echo data in a givenshort-distance section in the distance direction, and only using thesecond echo data in a given long-distance section in the distancedirection, for each direction (see FIG. 4). Here, the givenshort-distance section may be a section including the center of theradar image, and may be set so as to be substantially in agreement withthe blind zone of the modulated pulse signal. On the other hand, the“given long-distance section” as used herein may be a section which doesnot overlap with the given short-distance section and may be outwardlyadjacent to the given short-distance section in the distance direction.Hereinafter, the image data generated by the pulse synthesizing module24 c may be referred to as the “first image data V1.” In the radar imageof FIG. 4, echoes of ships may be expressed as E1, an echo of the raconmay be expressed as E2, and the response signal of the racon may beexpressed as E3.

Graph (C) of FIG. 5 illustrates a waveform of the first image data V1 ina direction indicated by an arrow D1 in FIG. 4, centering on the radardevice 1. Moreover, Graphs (A) and (B) of FIG. 5 illustrate waveforms ofthe first echo data and the second echo data which are used as the basisof the first image data V1 of Graph (C) of FIG. 5, respectively. Ashaving already described, as illustrated in Graph (B) of FIG. 5, thetarget objects which exist in the short-distance area cannot be acquiredby the second echo data, and the response signal of the racon cannotalso be acquired. On the other hand, as illustrated in Graph (A) of FIG.5, the S/N ratio falls in the long-distance area for the first echodata, compared with the second echo data, and therefore, the targetobject is displayed smaller. On the other hand, by using the first imagedata V1, the target objects in the short-distance area can be displayed,and the S/N ratio in the long-distance area is improved.

However, as illustrated in FIG. 4 and Graph (C) of FIG. 5, the responsesignal of the racon cannot be acquired in the long-distance area byusing the first image data V1. In FIG. 4 and Graph (C) of FIG. 5, theresponse signal which must have been displayed when the racon returnedthe response signal is illustrated by broken lines. Therefore, withoutdoing anything to this configuration, the crew cannot accurately graspthe existence of the racon in the distant location.

Therefore, in this embodiment, a second image data V2 (a display signalof the radar image) which is obtained by synthesizing the first imagedata V1 and the first echo data may be generated. In more detail, thecomparing module 24 d may compare, in the long-distance section, asignal intensity of the first image data V1 with a signal intensity ofthe first echo data for each direction, and generate the second imagedata V2 based on the results of the comparisons. At this time, for eachlocation in the distance direction within the long-distance section, thesignal intensity of the first image data V1 may be compared with thesignal intensity of the first echo data, and the display signal may begenerated based on the larger one among both the signal intensities.That is, by determining, for each location in the distance directionwithin the long-distance section, which signal intensity is largerbetween the first image data V1 and the first echo data, and couplingeach data of the larger signal intensity in the distance direction toeach other, the second image data V2 in the long-distance section may begenerated. On the other hand, as the second image data V2 in theshort-distance section, the first image data V1 in this section may beused as it is.

Note that the “signal intensities compared” as used herein do notnecessarily mean absolute signal intensities, and may mean relativesignal intensities on the basis of the intensities of the echo imagewhen converted into the echo image. That is, as for the unmodulatedpulse signal and the modulated pulse signal, the pulse compression maybe applied to the latter, even if the peak envelop powers are the same.For example, because of such a situation, the intensities of the echoimages cannot be compared even if the absolute signal intensities arecompared between the different kinds of signals. On the other hand, the“signal intensities” as used herein may be signal intensity on the basisof the intensity of the echo image indicated by the display signalconverted from the signal compared. For example, if a case where thesignal compared is converted into the display signal of 0 to 255 is usedas one example, the comparison can be made based on the intensity of theecho image indicated by the value of 0 to 255. Alternatively, the betterS/N ratio can also be determined to be the stronger signal intensity.

Graph (D) of FIG. 5 illustrates a waveform of the second image data V2when the first echo data and the first image data V1 of Graphs (A) and(C) of FIG. 5 are synthesized. Moreover, FIG. 6 illustrates a radarimage based on the second image data V2 after the above processing isapplied to the first image data V1 of FIG. 4. As illustrated in Graph(D) of FIG. 5, and FIG. 6, by the second image data V2, the targetobject which exists in the short-distance area can be acquired based onthe first echo data, and the response signal of the racon issuccessfully acquired based on the first echo data, regardless of theshort-distance area or the long-distance area. On the other hand, sincethe target object which exists in the long-distance area can be acquiredbased on the second echo data, its S/N ratio in the long-distance areamay be improved.

As described above, the second image data V2 may be generated based onthe first image data V1 in the short-distance area, and based on eitherone of the first image data V1 or the first echo data with larger signalintensity in the long-distance area. Note that the first image data V1in the short-distance section may be none other than the first echodata. Therefore, substantially, in the short-distance section, thesecond image data V2 may be generated based on the signal intensity ofthe first echo data, without using the second echo data. As alreadydescribed, this may be because the short-distance section corresponds tothe blind zone of the second echo data. Moreover, the first image dataV1 in the long-distance area may be none other than the second echodata. Therefore, substantially, in the long-distance area, the firstecho data may be compared with the second echo data, and the secondimage data V2 may be generated based on either one of the first echodata or the second echo data with larger signal intensity.

When the second image data V2 is generated, the rendering module 24 emay transfer to the display unit 21 the second image data V2 outputtedfrom the comparing module 24 d, while converting it into data of arectangular coordinate system (XY coordinate system) from data of apolar coordinate system (rθ coordinate system). The display unit 21 maydisplay the radar image based on the second image data V2 inputted fromthe rendering module 24 e.

<2. Generation of Radar Image>

As described above, the signal processing module 24 b, the pulsesynthesizing module 24 c, the comparing module 24 d, and the renderingmodule 24 e may collaboratively operate as an image generating module(which is also referred to as processing circuitry) 26 which generatesthe radar image based on the first reception signal and the secondreception signal which are received by the receiver 3. Below, a flow ofthe generation of the radar image by the image generating module 26described above is summarized with reference to FIG. 7.

First, at Step S1, the signal processing module 24 b may acquire thefirst reception signal received during the first receiving period,corresponding to a certain direction Dt, and may apply suitable signalprocessing to the first reception signal to generate the first echodata. At Step S2 which is executed in substantially parallel to Step S1,the signal processing module 24 b may acquire the second receptionsignal received during the second receiving period, substantiallycorresponding to the same direction Dt, and apply suitable signalprocessing to generate the second echo data.

At the subsequent Step S3, the pulse synthesizing module 24 c maygenerate the first image data V1 extending in the distance direction ofthe direction Dt based on the first echo data and the second echo datacorresponding to the direction Dt. The display signal corresponding tothe short-distance section in the distance direction of the direction Dtmay be determined according to the signal intensity of the first echodata of the first image data V1. On the other hand, the display signalcorresponding to the long-distance section in the distance direction ofthe direction Dt may be determined according to the signal intensity ofthe second echo data of the first image data V1. Note that a value ofthe display signal may be determined so that it is displayed moreclearly or more deeply on a screen as the signal intensity of the echodata which is the basis of the value increases. Note that, as alreadydescribed, although the display signal becomes the same value, theabsolute value of the signal intensity of the first echo data which isthe basis of the value may not necessarily become the same as theabsolute value of the signal intensity of the second echo data.

At the subsequent Step S4, the comparing module 24 d may generate thesecond image data V2 extending in the distance direction of thedirection Dt based on the first image data V1 and the first echo datacorresponding to the direction Dt. As for the part of the second imagedata V2 which corresponds to the short-distance section in the distancedirection of the direction Dt, the first image data V1 of this section,i.e., the first echo data of this section, may be applied. That is, thedisplay signal of the second image data V2 which corresponds to theshort-distance section in the distance direction of the direction Dt maybecome a value determined according to the signal intensity of the firstimage data V1, i.e., the signal intensity of the first echo data. On theother hand, the display signal of the second image data V2 whichcorresponds to the long-distance section in the distance direction ofthe direction Dt may be determined by a comparison of the signalintensity of the first image data V1, i.e., the signal intensity of thesecond echo data, with the signal intensity of the first echo data. Inmore detail, this display signal may be determined according to thelarger signal intensity, as the result of the comparison of the signalintensities. Note that the value of the display signal may be determinedso as to be displayed more clearly or more deeply on a screen as thesignal intensity of the image data which is the basis of the valueincreases.

At the subsequent Step S5, the rendering module 24 e may convert thesecond image data V2 in the direction Dt generated at Step S4 from dataof the polar coordinate system into data of the rectangular coordinatesystem. Then, in the subsequent Step S6, the rendering module 24 e mayupdate an image of an area of the radar image displayed on the displayunit 21 which extends in the direction Dt based on the converted secondimage data V2 in the direction Dt.

The processing Steps S1-S6 may be repeatedly executed for the subsequentdirection until a termination of the indication of the radar image iscommanded by a user via the user interface 22, for example (Steps S7 andS8). Note that the subsequent direction may be a direction which isadjacent to the current direction in a rotating direction of the radarantenna 10. When the termination of the indication of the radar image iscommanded, this processing may be ended.

<3. Modifications>

As described above, although one embodiment of the present disclosure isdescribed, the present disclosure is not limited to the above embodimentand is possible to be variously changed without departing from thespirit of the present disclosure. For example, the following changes arepossible. Moreover, the configurations of the following modificationsmay be suitably combined.

<3-1>

In the above embodiment, the generation of the radar image by the imagegenerating module 26 may be digital processing executed by the CPU 30which executes the program 40. However, all or part of the processingmay also be executed by FPGA (Field-Programmable Gate Array) withoutlimiting to the CPU, or may be analog-processed by analog circuitry.

<3-2>

In the above embodiment, the second image data V2 may be generated basedon the first echo data in the short-distance area, and in thelong-distance area, the first echo data is compared with the second echodata and the second image data V2 may be generated based on either oneof the first echo data or the second echo data with larger signalintensity. However, the first echo data may be compared with the secondecho data in all the sections in the distance direction, and the secondimage data V2 may be generated based on either one of the first echodata or the second echo data with larger signal intensity. In theshort-distance area, since the signal intensity of the first echo datanormally exceeds the signal intensity of the second echo data, asubstantially similar radar image can be finally obtained also in thiscase.

<3-3>

In the above embodiment, the first image data V1 may be generated basedon the first echo data in the short-distance section, and based on thesecond echo data in the long-distance section. However, if the imagebased on the first echo data and the image based on the second echo dataare suddenly switched therebetween in the radar image, a boundary linebetween both the images may be exaggerated, and therefore, an unnaturalradar image may be generated as a whole. Therefore, in order toeliminate the unnatural boundary line, the first image data V1 may begenerated as follows. That is, the first image data V1 can be generatedbased on the first echo data in the short-distance section, based on asynthetic signal of the first echo data and the second echo data in amiddle-distance section, and based on the second echo data in thelong-distance section. Note that the “middle-distance section” as usedherein may be a section closer in the distance direction to the centerof the radar image than the long-distance section and more distant fromthe center of the radar image than the short-distance section, and thethree sections may be adjacent to each other and do not overlap witheach other. The synthetic signal of the first echo data and the secondecho data for the middle-distance section can be generated by addingboth the data with weights according to the distances. FIG. 8illustrates a graph illustrating the weights (mixing ratio) which can beused for the weighted addition.

In this modification, upon generating the second image data V2 (thedisplay signal of the radar image) in each direction, for example, thecomparing module 24 d can compare the signal intensity of the firstimage data V1 with the signal intensity of the first echo data in thelong-distance and middle-distance sections, and can generate the displaysignal based on the larger signal intensity. In this case, in themiddle-distance section, the display signal of the second image data V2may be generated according to a larger one of the signal intensity ofthe first image data V1, i.e., the signal intensity of the syntheticsignal of the first echo data and the second echo data, and the signalintensity of the first echo data. On the other hand, in thelong-distance section, the display signal of the second image data V2may be substantially generated, similar to the above embodiment,according to the larger one of the signal intensity of the first echodata and the signal intensity of the second echo data.

<3-4>

In the above embodiment, upon generating the second image data V2 of thelong-distance section (and the middle-distance section in themodification 3-3) in each direction, the signal intensity of the firstecho data may be compared with the signal intensity of the first imagedata V1, and the display signal may be generated by selecting the largerone. However, for this section in each direction, the first echo datamay be compared with the first image data V1, and the display signal ofthe second image data V2 may be generated by adding both the data sothat the mixed ratio of the larger one becomes larger as the result ofthis comparison.

<Terminology>

It is to be understood that not necessarily all objects or advantagesmay be achieved in accordance with any particular embodiment describedherein. Thus, for example, those skilled in the art will recognize thatcertain embodiments may be configured to operate in a manner thatachieves or optimizes one advantage or group of advantages as taughtherein without necessarily achieving other objects or advantages as maybe taught or suggested herein.

All of the processes described herein may be embodied in, and fullyautomated via, software code modules executed by a computing system thatincludes one or more computers or processors. The code modules may bestored in any type of non-transitory computer-readable medium or othercomputer storage device. Some or all the methods may be embodied inspecialized computer hardware.

Many other variations than those described herein will be apparent fromthis disclosure. For example, depending on the embodiment, certain acts,events, or functions of any of the algorithms described herein can beperformed in a different sequence, can be added, merged, or left outaltogether (e.g., not all described acts or events are necessary for thepractice of the algorithms). Moreover, in certain embodiments, acts orevents can be performed concurrently, e.g., through multi-threadedprocessing, interrupt processing, or multiple processors or processorcores or on other parallel architectures, rather than sequentially. Inaddition, different tasks or processes can be performed by differentmachines and/or computing systems that can function together.

The various illustrative logical blocks and modules described inconnection with the embodiments disclosed herein can be implemented orperformed by a machine, such as a processor. A processor can be amicroprocessor, but in the alternative, the processor can be acontrolling module, microcontrolling module, or state machine,combinations of the same, or the like. A processor can includeelectrical circuitry configured to process computer-executableinstructions. In another embodiment, a processor includes an applicationspecific integrated circuit (ASIC), a field programmable gate array(FPGA) or other programmable device that performs logic operationswithout processing computer-executable instructions. A processor canalso be implemented as a combination of computing devices, e.g., acombination of a digital signal processor (DSP) and a microprocessor, aplurality of microprocessors, one or more microprocessors in conjunctionwith a DSP core, or any other such configuration. Although describedherein primarily with respect to digital technology, a processor mayalso include primarily analog components. For example, some or all ofthe signal processing algorithms described herein may be implemented inanalog circuitry or mixed analog and digital circuitry. A computingenvironment can include any type of computer system, including, but notlimited to, a computer system based on a microprocessor, a mainframecomputer, a digital signal processor, a portable computing device, adevice controlling module, or a computational engine within anappliance, to name a few.

Conditional language such as, among others, “can,” “could,” “might” or“may,” unless specifically stated otherwise, are otherwise understoodwithin the context as used in general to convey that certain embodimentsinclude, while other embodiments do not include, certain features,elements and/or steps. Thus, such conditional language is not generallyintended to imply that features, elements and/or steps are in any wayrequired for one or more embodiments or that one or more embodimentsnecessarily include logic for deciding, with or without user input orprompting, whether these features, elements and/or steps are included orare to be performed in any particular embodiment.

Disjunctive language such as the phrase “at least one of X, Y, or Z,”unless specifically stated otherwise, is otherwise understood with thecontext as used in general to present that an item, term, etc., may beeither X, Y, or Z, or any combination thereof (e.g., X, Y, and/or Z).Thus, such disjunctive language is not generally intended to, and shouldnot, imply that certain embodiments require at least one of X, at leastone of Y, or at least one of Z to each be present.

Any process descriptions, elements or blocks in the flow views describedherein and/or depicted in the attached figures should be understood aspotentially representing modules, segments, or portions of code whichinclude one or more executable instructions for implementing specificlogical functions or elements in the process. Alternate implementationsare included within the scope of the embodiments described herein inwhich elements or functions may be deleted, executed out of order fromthat shown, or discussed, including substantially concurrently or inreverse order, depending on the functionality involved as would beunderstood by those skilled in the art.

Unless otherwise explicitly stated, articles such as “a” or “an” shouldgenerally be interpreted to include one or more described items.Accordingly, phrases such as “a device configured to” are intended toinclude one or more recited devices. Such one or more recited devicescan also be collectively configured to carry out the stated recitations.For example, “a processor configured to carry out recitations A, B andC” can include a first processor configured to carry out recitation Aworking in conjunction with a second processor configured to carry outrecitations B and C. The same holds true for the use of definitearticles used to introduce embodiment recitations. In addition, even ifa specific number of an introduced embodiment recitation is explicitlyrecited, those skilled in the art will recognize that such recitationshould typically be interpreted to mean at least the recited number(e.g., the bare recitation of “two recitations,” without othermodifiers, typically means at least two recitations, or two or morerecitations).

It will be understood by those within the art that, in general, termsused herein, are generally intended as “open” terms (e.g., the term“including” should be interpreted as “including but not limited to,” theterm “having” should be interpreted as “having at least,” the term“includes” should be interpreted as “includes but is not limited to,”etc.).

For expository purposes, the term “horizontal” as used herein is definedas a plane parallel to the plane or surface of the floor of the area inwhich the system being described is used or the method being describedis performed, regardless of its orientation. The term “floor” can beinterchanged with the term “ground” or “water surface.” The term“vertical” refers to a direction perpendicular to the horizontal as justdefined. Terms such as “above,” “below,” “bottom,” “top,” “side,”“higher,” “lower,” “upper,” “over,” and “under,” are defined withrespect to the horizontal plane.

As used herein, the terms “attached,” “connected,” “mated,” and othersuch relational terms should be construed, unless otherwise noted, toinclude removable, moveable, fixed, adjustable, and/or releasableconnections or attachments. The connections/attachments can includedirect connections and/or connections having intermediate structurebetween the two components discussed.

Numbers preceded by a term such as “approximately,” “about,” and“substantially” as used herein include the recited numbers, and alsorepresent an amount close to the stated amount that still performs adesired function or achieves a desired result. For example, the terms“approximately,” “about,” and “substantially” may refer to an amountthat is within less than 10% of the stated amount. Features ofembodiments disclosed herein are preceded by a term such as“approximately,” “about,” and “substantially” as used herein representthe feature with some variability that still performs a desired functionor achieves a desired result for that feature.

It should be emphasized that many variations and modifications may bemade to the above-described embodiments, the elements of which are to beunderstood as being among other acceptable examples. All suchmodifications and variations are intended to be included herein withinthe scope of this disclosure and protected by the following claims.

What is claimed is:
 1. A radar device, comprising: a transmitterconfigured to transmit a first pulse signal and a second pulse signal, apulse width of the second pulse signal being wider than a pulse width ofthe first pulse signal; a receiver configured to receive a firstreception signal including a reflection signal of the first pulse signaland a second reception signal including a reflection signal of thesecond pulse signal; and processing circuitry configured to: compare, ina first section that is at least partly in a distance direction, asignal intensity of the first reception signal with a signal intensityof the second reception signal, generate a display signal based on aresult of the comparison in the first section, compare a signalintensity of a synthetic signal of the first reception signal and thesecond reception signal with the signal intensity of the first receptionsignal in a second section closer to a transmitting location than thefirst section, and generate the display signal based on a result of thecomparison in the second section.
 2. The radar device of claim 1,wherein the processing circuitry is further configured to: generate thedisplay signal in the first section based on the first reception signalwhen the first reception signal has a larger signal intensity than thesecond reception signal; and generate the display signal in the firstsection based on the second reception signal when the second receptionsignal has a larger signal intensity than the first reception signal. 3.The radar device of claim 1, wherein the processing circuitry is furtherconfigured to: generate the display signal in the second section basedon the synthetic signal when the synthetic signal has a larger signalintensity than the first reception signal; and generate the displaysignal in the second section based on the first reception signal whenthe first reception signal has a larger signal intensity than thesynthetic signal.
 4. The radar device of claim 3, wherein the firstpulse signal has a pulse width of less than 2 microseconds, and thesecond pulse signal has a pulse width of 2 microseconds or longer. 5.The radar device of claim 4, wherein the transmitter is installed on aninstallation surface, and transmits through an antenna configured torotate in a plane parallel to the installation surface.
 6. The radardevice of claim 5, wherein the first pulse signal is an unmodulatedsignal and the second pulse signal is a modulated signal.
 7. The radardevice of claim 6, wherein the radar device is a solid-state radar. 8.The radar device of claim 1, wherein the first pulse signal has a pulsewidth of less than 2 microseconds, and the second pulse signal has apulse width of 2 microseconds or longer.
 9. The radar device of claim 1,wherein the transmitter is installed on an installation surface, andtransmits through an antenna configured to rotate in a plane parallel tothe installation surface.
 10. The radar device of claim 1, wherein thefirst pulse signal is an unmodulated signal and the second pulse signalis a modulated signal.
 11. The radar device of claim 1, wherein theradar device is a solid-state radar.
 12. A method of generating a radarimage, comprising: transmitting a first pulse signal and a second pulsesignal, a pulse width of the second pulse signal being wider than apulse width of the first pulse signal; receiving a first receptionsignal including a reflection signal of the first pulse signal and asecond reception signal including a reflection signal of the secondpulse signal; comparing, in a first section that is at least partly in adistance direction, a signal intensity of the first reception signalwith a signal intensity of the second reception signal; generating adisplay signal based on a result of the comparison in the first section,comparing a signal intensity of a synthetic signal of the firstreception signal and the second reception signal with the signalintensity of the first reception signal in a second section closer to atransmitting location than the first section, and generating the displaysignal based on a result of the comparison in the second section.
 13. Anapparatus comprising: a processor, and a memory having stored thereoncomputer-executable instructions which, when executed by the processor,cause the apparatus to: transmit a first pulse signal and a second pulsesignal, a pulse width of the second pulse signal being wider than apulse width of the first pulse signal; receive a first reception signalincluding a reflection signal of the first pulse signal and a secondreception signal including a reflection signal of the second pulsesignal; compare, in a first section that is at least partly in adistance direction, a signal intensity of the first reception signalwith a signal intensity of the second reception signal; and generate adisplay signal based on a result of the comparison in the first section,compare a signal intensity of a synthetic signal of the first receptionsignal and the second reception signal with the signal intensity of thefirst reception signal in a second section closer to a transmittinglocation than the first section, and generate the display signal basedon a result of the comparison in the second section.